F.lux for Mac 5.0

At a Glance

Some of today’s LCD displays are so bright they can be uncomfortable to look at—especially at night. I’ve covered several utilities for adjustingyour screen’s brightness beyond the normal hardware and software controls, but most of these utilities focus on simply reducing brightness. As it turns out, there's more to display-viewing fatigue than brightness.

If, like me, you tend to occasionally work (or play) in front of your computer late at night, you may find it difficult to sleep soon after. According to a good amount of research, part of the problem is that bright light—and especially bright light of particular color temperatures—keeps your brain from progressing through its normal “it’s getting later in the day, lets start winding down” process. (This is the layman’s description, of course.) Thus, it should come as no surprise that looking at a computer display late at night—particularly when that display is calibrated to be bright and clear during the daytime—can be both visually irritating and a contributor to sleep problems.

One treatment for people who have trouble getting to sleep at night is a purposeful evening shift from bright, higher-temperature (bluer) lighting to softer, lower-temperature (warmer/redder) lighting. F.lux aims to mimic this natural transition on your computer’s screen.

When you launch F.lux, it asks to use your location to determine the local times for sunrise and sunset. You then choose the type of nighttime lighting you use in the room hosting your computer: tungsten, halogen, fluorescent, or daylight (light that mimics sunlight). A Preview button shows you how the screen will look when dimmed for the chosen type of lighting—I recommend using the preview feature at night, in the target lighting, rather than during the day. (The developer says you should choose the setting that makes an onscreen document look “like the pages of a book under your room lights.”)

After that simple setup, F.lux sits in the background, waiting for sunset. Once the sun starts to go down, the utility gradually—over the course of an hour—dims your screen and shifts its color temperature to match that of the type of lighting in the room. (You can opt for this change to happen quickly, but I find the hour-long transition to be much less jarring.) Similarly, if your computer is in use at sunrise, F.lux gradually brightens the screen and shifts its color temperature back to normal.

I’ve definitely found my big, bright iMac screen to be more comfortable to look at late at night when using F.lux—the display simply “matches” the ambient lighting better. And although I haven’t done any controlled experiments, it seems to me that I’m less wide-eyed and wired when I turn off the computer. It did take me a couple nights to get used to the different color balance of my F.lux-dimmed displays, though.

When using F.lux, you can still adjust your display’s brightness separately if you find F.lux’s dimming to be too dramatic (or too limited). Unfortunately, you can’t fine-tune the specific temperature settings to better match the lighting of a particular room. Another limitation is that although F.lux’s systemwide menu lets you disable the utility for an hour—to do some work that requires color accuracy, or just to temporarily perk up when working on something especially tedious—there’s no way to adjust that period of time if, say, you plan to watch a movie for two hours. The workaround is to quit F.lux and relaunch it later.

The F.lux Website notes that the developers are working on some of these minor issues. But even without those improvements, if you occasionally—or regularly—burn the midnight oil, F.lux makes those late nights easier on your eyes, and possibly on your sleep cycles.